1. Field of the Invention
The invention relates to an improved material handling or treating plow blade and mounting structure therefor that are attachable to a tractor, snow grooming vehicle, and similar self-propelled vehicles. The plow blade may be a scraper blade, a snow plow blade, or other plow blade for which, in operation, there is required adjustability in the height of the blade above the terrain, and adjustability, also, in the cutting angle or angle of attack of the blade in three dimensions, that is along three separate pivotal axes each of which is spaced 90.degree. from the others.
2. Description of the Prior Art
Different forms of mounting structures for material handling or treating plow blades have been proposed in the prior art for providing height and three dimensional blade adjustability. One form disclosed in U.S. Pat. No. 3,157,099, granted Nov. 17, 1964, utilizes a C-frame pivotally mounted on a tractor and a two-section plow blade, a three-section plow blade being suggested but neither illustrated nor otherwise described, attached at a vertically hinged connection of the blade sections by a pivot pin or pintle to the C-frame, the pintle extending centrally and longitudinally of the tractor. The main thrust of the load on the plow blade is concentrated on the pintle connection to the C-frame. Therefore, in order to provide the essential strength the C-frame necessarily must be massive and heavy. As a result, the mounting structure is costly to manufacture and difficult to assemble. Moreover, special hydraulically actuated rams are needed to support and adjust the ends of the plow blade sections, further adding undesirably to the difficulty and cost of manufacture and assembly.
Another form of mounting structure for a material treating plow blade is disclosed in U.S. Pat. No. 3,822,751, granted July 9, 1974. The structure there shown provides, for a single section plow blade, adjustability in height and cutting angle in three planes, and comprises an assembly of five different frames that are pivotally connected to each other, the connection of the second and third frames to each other being by a single centrally located vertically disposed pivot carried at the vertex of a triangular portion of the second frame. The first frame is attached to a tractor and the fifth frame to the plow blade. Here, too, the main thrust of the load on the plow blade is concentrated on a single pivot, the vertically-disposed pivot connection between the second and third frames. This requires those frame, particularly, to be massive and heavy, adding further to the difficulty and cost of manufacture and assembly of a complex assortment of frames.
While the mounting structures of U.S. Pat. Nos. 3,157,099 and 3,822,751 both provide for height and three dimensional adjustability of the plow blade, the structures are such that adjustment of the blade height, in each case, undesirably alters the pitch or roll angle of the blade. Accordingly, a compensating pitch angle adjustment is required whenever the height of the blade is changed if the optimum pitch angle for the resistance characteristics of the material being handled or treated is to be maintained.
Three-section forms of plow blades for attachment to a tractor are disclosed in U.S. Pat. Nos. 3,477,151, granted Nov. 11, 1969 and 4,019,268, granted Apr. 26, 1977. Specifically, U.S. Pat. No. 3,477,151 shows a snow plow comprising a center or primary blade and two wings or flanking auxiliary blades, each pivotally connected about an upright or vertical axis at an associated end of the center blade, the manner of attachment of the snowplow to a self-propelled vehicle not being shown. The wing blades are connected for simultaneous limited inverse pivotal movement with respect to the center blade, from relative positions wherein one wing blade is aligned with the center blade when the other is at an angle rearward of less than 180.degree. therewith. Forward pivotal movement of the wing blades with respect to the center blade is not permitted.
U.S. Pat. No. 4,019,268 shows a three-section plow blade for snow compacting equipment in which the blade is pivotally secured to a vehicle by first and second frames parallel to the blade and by a pair of third frames that extend normal to the second frame. The three-section blade includes a center blade and two wing blades, each pivotally connected to an associated end of the center blade. The pivotal connections are horizontal whereby the wing blades, when actuated relatively to the center blade, pivot upwardly. This facilitates transportation of the equipment to and from ski trails and for storage when not in use. The structure does not provide for either downward, rearward or forward pivotal movement of the wing blades with respect to the center blade.
Accordingly, there still exists a need for improvements in the mounting structures or assemblies for plow blades, particularly in respect to an arrangement for a plow blade having variably adjustable wings: (a) that simplifies the construction and reduces the size and weight of the components while maintaining the essential structural strength, reduces the number of component parts and their manufacturing and assembly cost; (b) wherein the height adjustment of the plow blade is substantially independent of the cutting angle adjustments thereof, and in particular, the pitch or roll angle adjustment, and (c) wherein the adjustable wings of the plow blade have greater freedom of movement independently of each other, including forward as well as rearward pivotal movement with respect to the center blade.